Traffic control system for selection among multiple offsets and multiple cycle lengths in response to the levels of two measured traffic characteristics



3,241,107 E OFFSETS March 15, 1966 c. L. DU VIVIER TRAFFIC CONTROL SYSTEM FOR SELECTION AMONG MULTIPL AND MULTIPLE CYCLE LENGTHS IN RESPONSE TO THE LEVELS OF TWO MEASURED TRAFFIC CHARACTERISTICS Filed Sept. 18, 1961 5 Sheets-Sheet 2 P5050 mozmmwmhza ZNVENTOR CHARLES L. DUVlVIER ATTORNEY 3,241,107 E OFFSETS March 15, 1966 c. L. DU VIVIER TRAFFIC CONTROL SYSTEM FOR SELECTION AMONG MULTIPL AND MULTIPLE CYCLE LENGTHS IN RESPONSE TO THE LEVELS OF TWO MEASURED TRAFFIC CHARACTERISTICS Filed Sept. 18, 1961 5 Sheets-Sheet 5 NdI INVENTOR. CHARLES L. DUVIVIER ATTORNEY March 15, 1966 c. L. DU VIVIER 3,241,107

TRAFFIC CONTROL SYSTEM FOR SELECTION AMONG MULTIPLE OFFSETS AND MULTIPLE CYCLE LENGTHS IN RESPONSE TO THE LEVELS OF TWO MEASURED TRAFFIC CHARACTERISTICS Filed Sept. 18, 1961 5 Sheets-Sheet 4 l l 3 5| 0 l SPLIT SELECTION m I NETWORKS 1 I 1 355-356 1 I I E i l o i 9 i I I I TO FIG.4

FIG.3

INVENTOR. CHARLES L. DU VIVIER ATTORNEY c. DU VIVIER 3,241,107 0R SELECTION AMONG MULTIPLE OFFSETS March 15, 1966 TRAFFIC CONTROL SYSTEM F AND MULTIPLE CYCLE LENGTHS IN RESPONSE TO THE LEVELS OF TWO MEASURED TRAFFIC CHARACTERISTICS Filed Sept. 18, 1961 5 Sheets-Sheet 5 MOTOR VEHICLE DETECTOR 1 SPLlTSELECTlON FROM FIG 3 INVENTOR CHARLES L.DuV|v:ER

FSGA

ATTORNEY United States Patent 0,

3,241,107 TRAFFIC CONTROL SYSTEM FOR SELECTION AMONG MULTIPLE OFFSETS AND MULTI- PLE CYCLE LENGTHS IN RESPONSE TO THE LEVELS OF TWO MEASURED TRAFFIC CHARACTERISTICS Charles L. Du Vivier, Darien, Conan, assignor to Laboratory for Electronics, Inc., Boston, Mass, a corporation of Delaware Filed Sept. 18, 1961, Ser. No. 138,827 7 Claims. (Cl. 340-36) This invention relates to an improved traffic actuated control system of the master-local controller type and particularly to greatly improved actuated control apparatus including a master controller for use in a traflic control system, which is responsive to trafiic actuation, and local controllers, which may be trafhc actuated or nontraffic actuated but yet responsive, when desired, to con trol of a master controller, in varying degrees of control, upon predetermined traffic conditions of the roadway over which the traific is traveling.

In order to provide an efficient operating master-local tratlic control system it is desirable to provide at least a common control function to all local controllers in the control system from the master controller to which the local controllers may respond in common. One such control is referred to as a coordination or synchronization control which, in effect, provides a supervisory function over the local controllers and keeps the local controllers in-step. This does not necessarily mean simultaneous operation of the local controllers although such coordination control may be employed to provide simultaneous operation.

A common coordination control may be used to maintain the signal cycles of adjacent local controllers at certain relationships with each other, which is accomplished by establishing desired individual displacements of the local controller cycles from the master cycle as a reference, this displacement of the local cycle from the reference being commonly referred to as the offset. During simultaneous operation of the local controllers, that is with the green signals changing at all controllers simultaneously, it may be considered that no offset of the signal cycle is in effect or that all of the controllers have a zero offset.

It has been found, in the field of traffic control, that three basic offset conditions may be efficiently employed in a traffic control system. These three basic offset conditions may be based on the relative difference or a predetermined differential between the value or count of traffic characteristic of traffic volume for example. For convenience of description these three basic offset conditions will be referred to as average offset or average, which may prevail when both traffic flows are substantially equal, or unequal but are within a predetermined difference in value, inbound offset or inboun which may prevail when the inbound traffic flow exceeds the outbound traffic flow by a predetermined value, for example, and outbound offset or outbound may prevail when the outbound traffic flow exceeds the inbound traffic flow by a predetermined value.

It should be noted that the mentioned offsets are basic offsets and each may be further broken down into degrees of traffic offset conditions depending upon the offset conditions and the total amount of the traffic on the entire roadway, such as, for example, light traffic, average offset, when both traffic flows are substantially equal and the total traffic is light, medium traffic, average offset, when both traffic flows are substantially equal and the total traffic on the roadway is medium or moderate, and heavy traffic, average offset, when traffic flows are 3,241,197 Patented Mar. 15, 1966 substantially equal and the total traffic is heavy, and so forth.

The relative traffic offset conditions may also be broken down on a finer basis, if it be desired, such as on a percentage basis using a predetermined number of vehicles in the traffic flow as percent and determining the percentage proportionally, with the number of vehicles.

A percentage of traffic value may be based on a count over a substantially short sampling time period as for example six to ten minutes and may indicate zero percent when no vehicles are counted on the roadway during the sampling period, for example, and may indicate 100% when a predetermined number of vehicles is counted during the sampling period. The predetermined number of vehicles representing 100% may be the number of vehicles that the roadway was designed to carry as full capacity. Obviously, the one hundred percent value of traffic on a roadway may mean that the traffic count or value is such that the number of vehicles present on the roadway is all that the roadway is capable of handling and still maintain reasonable traffic flow.

A percentage of traffic above one hundred percent, may mean that the number of vehicles present on the roadway is in excess of the number of vehicles the roadway was designed to carry.

Relative traflic conditions on a roadway may be made to affect a traffic control system in different ways, as for example, with an offset condition of average, inbound or outbound determined by the differential between two measured traffic flows, the percentage of offset between adjacent controllers may be made variable relative to the volume of the highest traffic flow or aggregate of the traffic flows on the roadway.

Various percentage of offset between adjacent controllers may be locally adjusted but may be remotely selected according to either the percentage of the higher of the two traffic flows or according to the percentage of the total traffic fiow. This condition is more easily understood relative to inbound and outbound offset conditions than average offset conditions since average offset may very often provide balanced or simultaneous operation of the local controllers. While both inbound and outbound offset may shift the signal cycle of adjacent controllers so that the start of the signal cycle of one local controller is offset with respect to the start of the signal cycle of another local controller the degree of offset may be varied according to the amount of traffic.

Traffic value or count on a roadway may also affect a traffic control system by varying the length of the signal cycle, as for example, light traffic conditions may provide a short signal cycle and, as the traffic count increases, the length of the signal cycle may vary accordingly, as desired, either proportionally or non-proportionally, with the count or measurement. The length of the traffic signal cycle may also vary or be varied according to the trafhc volume attaining a certain predetermined value or level, with as many levels as desired for varying the signal cycle length, as desired.

Further, a combination of prevailing traffic conditions on a roadway, such as relative traffic conditions between traffic flows and traflic value or count may be employed to provide various changes in a traffic control system. As for example, the combination of the two factors of relative conditions between traffic flows and traffic value or count of the higher of the two traffic flows above may be used to vary uniformly the length of the signal cycle. Along these lines, the length of the signal cycle may be varied according to the offset condition prevailing with the offset condition controlled by the combination of relationship between the two traffic flows plus the value of the higher of the two traffic fiows and the degree of offset controlled solely by the total traffic value or count.

Further the offset condition may be controlled solely by relationship between two traflic flows and the signal cycle length may vary solely according to the value or count of the higher of the two traflic flows with the degree or amount of offset varied according to the length of the signal cycle selected. Thus, in the latter mode of operation, a predetermined relationship between the degree or percentage of offset and the length of the signal cycle may be maintained although the offset condition and the signal cycle length may be determined independently of each other.

This latter effect of traffic conditions such as the value of traflic flow measurements and relationship between trafiic flows in a trafiic control system may provide for an extremely versatile and flexible control system when the traffic flow measurements and the relationship between traffic flows are representative of the substantially cuirent traflic flow on the roadway. Effect of substantially current trafiic conditions on traffic control systems has been substantially limited to relatively highly complex, expensive and massive electronic and electro-magnetic equipment.

Such complex and massive electronic and electro-magnetic equipment has certain disadvantages since the cost of procurement of such equipment is substantially high and such expenditure may be justified by extensive and far reaching use of the same, such as in relatively large traflic control systems which may employ, many local controllers supervised by one master controller. Further, installation and maintenance of this complex master controller and system occasionally presents other problems since highly skilled technicians are usually required to install, maintain and repair the master controller and the local controllers of the traffic control system. The massiveness also presents a problem of storage.

The present invention provides a greatly improved master controller in part electronic and in part electro-magnetic, responsive to substantially current demands of trafiic, such demands determined through actuation of a sampling of at least two traflic flows one one or more roadways. The electronic part of the master controller may be provided as a substantially simplified counting or measuring device such as a simplified trafiic volume counting circuit or a simplified trafiic density determining circuit or a simplified trafiic speed averaging circuit or other simplified circuit to measure or determine any other characteristic of a traflic flow, each of which may be operated and the value or count determined by actuation of a sampling of the-vehicles in the traffic flow.

The preferred embodiment of the improved master controller includes two identical traflic flow characteristic determining and measuring units, as'for example traflic volume determining and measuring units, each of which may determine the volume of traffic, for example, on one or more trafiic lanes of one or more substantially similar trafiic flows and maintain a substantially running count, measurement or value of trafiic volume, for example, so that the two separate counts, measurements or values of a similar trafiic characteristic are of substantially current traffic. Associated with each determining and measuring unit is a comparingunit, each of which is interlocked with the measuring unit with which his not associated.

As will be more fully described with reference to the accompanying drawing, the trafiic characteristic determining and measuring unit of each traflic characteristic determining, measuring and comparing component senses and measures, through actuation of a sampling of the lehicles in the traffic flow, the traflic characteristic to be letermined and measured. Such traffic characteristic nay be the volume of trafiic the measurement of which nay be calibrated in vehicles per unit time, or traffic lensity, calibrated in the number of vehicles per unit ength of roadway, or average speed of the trafhc flow, :alibrated in miles per hour.

The output of each trafiic (D.C.) voltage which may vary from 0 to volts and may represent from O to 100% of a predetermined value of the trafiic characteristic determined. Each D.C. voltage from each measuring unit is applied to several associated individually adjusted level response or pick-off circuits which make up the preferred form of comparing unit and each D.C. voltage is also applied to one of the response circuits of the other comparing unit to become a reference from which a predetermined differential betwen the two D.C. voltages may be determined.

TRAFFIC LEVEL RESPONSE CIRCUITS-GENERAL Each traflic characteristic comparing unit includes an identical number of individual level response circuits, each of which may be individually adjusted to respond to a predetermined level or value of the D.C. output and further, to stop responding at another separately adjustable level or value of the same D.C. voltage.

As described below the preferred embodiment of master controller is provided with at least two vehicle detection or vehicle actuated input circuits, with at least one input circuit for each trafiic characteristic, for example volume, determining unit, two separate and identical traflic volume determining and measuring units and a comparison unit including at least four dual-adjustable level response circuits, associated with each volume determining unitl Each level response circuit is connected to the output of its associated measuring unit, with one of the level circuits of each comparison unit connected to the output of the measuring unit of the other determining, measuring and comparing component. Thus the D.C. voltage output, representing one volume measurement of one measuring unit becomes a reference level for the level response circuit of the other determining, measuring and comparing component so that response to at least a predetermined differential between the two electrical values may be obtained by operation or response of one or the other of the correspondingly connected level response circuits or no response obtained from either of the level response circuits, according to the differential between the two electrical values.

The first, second and third of the series or response circuits may be adjusted so. that response may be sequentially provided by the first, then the second and then the third response circuit, etc., as the level of the associated D.C. voltage increases, with the individual levels of response individually adjustable so that although the response may be made sequentially, the various levels at which the response circuits may respond need not be uniformly separated. Further, each of the response circuits are also adjustable so that cessation of response may be made at a different level than initiation of response of the same circuit.

Thus the improved master controllermay provide separate internal response to various levels of electrical energy, the value of which represents a level or volume of tralfic and also. may respond to the relation between two electrical energies which response may represent at least a predetermined differential between the two electrical energies. Response to various levels of each electrical energy may be individual to each determining, measuring and comparing component with or without uni form or similar differentials between the various levels of response. Response to a predetermined relationship or differential between the two electrical energies may be made without regard to the relative amplitude of the energies so long as the differential between the electrical values is at or exceeds a minimum preset value or differential.

RESPONSE TRANSLATING COMPONENT GENERAL The response reflected by the individual response circuits, which may represent current traffic conditions and current relation between the traflic flows, is applied to a simplified electro-magnetic response translating component. Since the trafiic value of both trafiic flows are independently represented and the relationship between the two traffic flows is also independently represented, the preferred embodiment provides that these representations, be translated and converted into an output from the master controller so that the output may represent current traffic conditions on the roadway.

The response translating component which is associated with the two trafiic characteristic determining, measuring and comparing components is arranged so that a mode of operation may be selected from a variety of modes of operation depending upon the degree of flexibility and versatility of the master controller desired.

Primarily the response translating component provides an output which may control one or more local controllers in a traffic control system by calling or demanding one or another general traffic plan, selected according to the general trafiic conditions on the roadway. The output is the output of the master controller of which each of the above mentioned components is a part. This output is extended to all the local controllers in the traflic control system and uniformly received. The output may be made up of a group of energized and/or deenergized leads, the combination of which may vary according to response by the comparing units and the mode of operation of the response translating component. Selection of one of several timing devices within the response translating component may be made according to response of the comparing units. The output of the master controller may be maintained for a period timed by the selectable timing device during which no change in output may occur but after which a change in output may occur according to translation of the response of the traffic characteristic detenmining, measuring and comparing components, at which time not only may the output the changed, but a new selection of a timing device may be made.

In the preferred embodiment of the master controller, a periodic coordination output pulse may be provided to all local controllers in the trafiic control system at all times when the master controller is in operation. This coordination output pulse may maintain coordination among the local controllers and between each local controller and the master controller, however, it may be desired to release one or more of the local controllers in the control system from coordinated operation. This may be accomplished by local adjustment of the individual controller. This provides for permitting isolated operation or setting free" of any one local controller in the control system without interfering with the coordinated operation of the other local controllers.

The output of the master controller also includes output leads for providing control of the offset of the signal cycle of each of the responsive local controllers. With respect to local controller response to the offset control output of the master controller, each local controller may respond independent of each other local controller and thus may be made to respond in a different degree to the same call or demand, depending upon local adjustment of the individual local controller. The section or part of the response translating component which provides the output for offset control includes the optional feature of providing a combination of available outputs which may demand or call for, what may be referred to as, free" operation of the local controllers under certain traflic conditions. Free operation may be the condition of operation Where no offset condition prevails, which may be desired during very light traffic conditions. free operation of the local controllers may be eliminated, so that one or the other offset condition maybe maintained at all times, as desired. Further, provision is made so that certain desired local controllers in the control system may go free while other local controllers may be in an offset condition in response to the same master controller output. It should be noted that the term free operation diifers from isolated operation in that during free operation the local controllers may still remain coordinated but in an isolated operated condition the local controller may be released from all master control.

The selection by the response translating component, of an offset condition, for output to the local controllers, may depend upon the relationship between the two trafiic flows, as expressed by the response of corresponding level response circuit of either one of the traffic characteristic determining, measuring and comparing component. The relationship between the two traffic flows is determined by using the level or value of electrical energy of one traffic characteristic determining, measuring and comparing component as a reference for the other traffic characteristic determining, measuring and comparing component, thus each electrical value may become a reference for the other electrical value and as such, response may be made by one or the other corresponding level response circuit to a preselected differential between the two electrical energies. Such response may be conditioned upon at least one electrical energy or voltage value or traffic level increasing to or above a minimum predetermined level, or response may be made directly upon one electrical value increasing above the other, to or above a predetermined differential between the two electrical values without regard to the actual level of electrical value or traffic level.

OFFSET CONTROL AND CYCLE LENGTH CON- TROL PARTS OF RESPONSE TRANSLATING COMPONENT The improved master controller herein presented further includes an additional feature heretofore unutilized in simplified master controllers of this general type. The current offset conditions are internally expressed in one part of the response translating component by application of power to one or more of several internal terminals, which power is applied through a network of circuitry controlled by the same response components by which olfset conditions are determined. Power applied to any one or more terminals may be applied to the second section or part of the response translating component through jumper connections adjusted as desired, so that certain desired signal cycle length control circuits, which provide one part of the total output of the master controller, may be associated with any one or more ofrset conditions so that the cycle length output control may be made to respond, as desired to the offset control part of the response translating component or may be made independent of the offset control part so that oifset control and cycle length are determined independent of each other or combined in varying degrees, as desired, so that varying degrees of flexibility of the master controller itself, are available through adjustment of the jumper connections between the two sections of the response translating component as desired.

Referring particularly to the second section of the re sponse translating component, this second section may be subdivided into three sub-sections, the first sub-section may be the timing section which may include three timing motors or synchrolizers," each of which may be selectable according to preselected traflic levels, and/or may be otherwise selected according to the mode of operation of the master controller, in cooperation with the first section as determined by the connections made by the jumper leads.

MODES OF OPERATION OF CYCLE LENGTH SEC- TION OF RESPONSE TRANSLATING COMPO- NENT vices or synchrolizers directly according to the level or value of traffic as determined by at least one of the trafiic volume determining, measuring and comparing :omponents. One synchrolizer out of three is selected, when both levels or values of traffiic volume are below Individually preselected minimum values respectively; another synchrolizer is selected when one or both levels are at or above an individually preselected minimum value out neither value is at or above individually preselected .naximum values and a third synchrolizer is selected when one or both levels are at or above individually prese- Lected maximum values of traffic volume.

Another mode of operation may provide selection of one or the other of the synchrolizers directly according the relationship between the two traffic flows without ."egard to the levels of traffic volume. A further mode of operation, as selected by the jumper connections between :he two parts or sections of the response translating comoonent, may provide for selection of one or the other of :he synchrolizers according to a selected combination of offset conditions and selected levels of traffic volume. An additional mode of operation provides for manual selec- Lion of one of the synchrolizers over the others, if desired.

Each synchrolizer may be adjusted to'complete a cycle of operation in a different length of time, as desired. Each synchrolizer controls a set of camsor cam contacts each set being substantially similar, with one pair of cams .n each set of contacts of each synchrolizer being part of 1 series circuit employed to energizea locking relay, when all the cam contacts are closed. At a predetermined part of each cycle of operation, as for example just prior to termination of each cycle of operation, the lock relay is operated by all the series connected contacts being closed. Operation of this relay permits translation to take place In the response translating component. During a certain part of the cycle of operation, as indicated onthe cam sequence chart among the several drawings, selection of one of the three synchrolizersis made, although the syn- :hrolizer selected may be the same synchrolizer which :ontrolled the last cycle, and the selected synchrolizer is initiated into operation while the other synchrolizers remain at rest. In addition, a coordination control'relay is released by the opening of another pair of cam contacts iust prior to termination of the cycle of operation of the operated synchrolizer. The coordination control relay :ontrols one of the output leads which may be deenergized for a short time and then energized thereafter. This :oordination output lead may initiate local controllers into operation and in effect start all the local controllers at the same time. The remainder of the output leads of the response translating component operate in conjunction with selection of a synchrolizer provide for selection of a cycle length control means, from several cycle'length control means in the local controller which controls the signal :ycle length of the local control. The remaining cams or :am contacts provide a self-driving circuit for self-operaion of the selectedsynchrolizer after the selected syn- :hrcTzeFIsTfEt-edinto"opcration-andqherr is -isolated from the initiating circuit.

During the period in which translation of response to :rafiic conditions is made the self-driving circuit cams are open and the selected synchrolizer is initiated into opera- :ion through selective circuitry in cooperation with con- :acts of the lock-relay, depending upon the mode of operation obtained by selectionof the jumper connections.

Cooperation between the synchrolizer controlled lock relay and the self driving cam contact is provided so that selection of one of the three synchrolizers and an associated output may be made only at termination of the cycle of operation of the last selected synchrolizer. One syn- :hrolizer is selected and initiated into operation after which the selected synchrolizer is electrically isolated from the selecting and initiating circuitry so that once selection of a synchrolizer is made, the master controller may not make another selection of synchrolizer and associated output for at least a minimum time period as timed by the selected synchrolizer.

The third sub-section of the second section includes the jumper connection leads and circuitry for translating the response of the second and third level response circuits of the traffic characteristic determining, measuring and comparing components.

Upon examination of the circuitry of this section of the response translating component, it may be readily seen that the type of final output of this improved master controller may be varied, as desired, so as to include the total possible output combinations of the five output leads or the output leads may be reduced in number so as to include output combinations of less than five leads. Further when the total possible output leads are employed one or more of a variety of modes of operation may be selected as described above.

From another aspect the present invention provides an improved master-local traffic control system employing a master controller including the features described above and further including local controllers which may be of the non-traflic actuated or may be of the semi-traffic actuated type local controller or may be of the full traflic actuated type local controller or any combination of two or more different types of local controllers included in the same traffic control system. However, although each of the local controllers may be of any one of the various types of local controllers mentioned, local controllers may be either twophase controllers, that is according control of traffic at an intersection of two roadways or two interfering traffic flows or three phase controllers, that is according control of traffic at three intersecting roadways or two intersecting roadways plus a pedestrian traffic movement, or three interfering traflic flows, each local controller in the traffic control system need be, in some degree responsive to actuation by the master controller.

COORDINATION UNIT AND SIGNAL SWITCHING CONTROL UNIT PARTS OF LOCAL CONTROLLER In the preferred embodiment of the improved masterlocal traffic control system the local traffic controllers may be divided into two parts, a first part which may be referred to as a coordination unit and a second part which may be referred to, for convenience, as a signal switching device or control unit. The signal switching device may itself be a fully integrated local controller and may be capable of independent or isolated operation so that control of right-of-way at the intersection over which it exerts control may be maintained without requiring control from the master controller or the coordination unit.

Each coordination unit of each local controller in a traflic control system is connected to the output leads extending from the master controller.

When operating in a fully coordinated master-local traffic control system, the coordination unit may respond to demand or call from the master controller to select an offset and signal cycle length from several locally adjusted offsets and from several signal cycle lengths. The master controller sends out, What'nray be general-lyrefecredatoitsmfi,

a coded output to each local controller in the traffic control system. Each different output combination or coded output from the master controller may represent a different demand to the local controllers and may be associated with, but not necessarily representing, a different condition of current traflic conditions. Upon initially receiving the particular output or demand from the master controller, each local controller interprets the coded output or demand and provides a trafiic plan individual to the particular local controller, such trafi'lc plan being preselected to be provided by the particular local controller upon receiving the particular coded output from the master controller. The particular traffic plan provided by any individual local controller may include a condition of offset of the signal cycle from a common part of the signal cycle of each local controller and/or a particular preselected 9 signal cycle length and/or a preselected distribution of cycle or split among the several phases, or a traffic plan excluding one or two of the enumerated features. The coordination unit receives the output of the master controller and interprets the particular output for that particular local controller.

The coordination unit, after interpreting the output of the improved master controller provides an output of its own and applies its output to the signal switching device which output may represent a certain preselected traffic signal plan of offset, signal cycle length and/or call for a certain preselected distribution of cycle or split of cycle from several splits of the cycle or any one or combination of two or combination of all three conditions, which may be individually preselected for providing more efficient flow of traffic at that intersection accordingly.

The preferred embodiment of the coordination unit may include three separate, independently operated, locally adjusted, remotely selectable signal cycle length timing means, one of which may be selected and operated to the exclusion of the other timing means according to the demand or call from the master controller and according to local adjustment of the coordination unit.

Each timing means may further be associated with several cams, each of which may be individually adjusted for providing a different offset condition. Thus each timing means may control a cam for providing average offset, a cam for providing inbound offset, and a cam for providing outbound offset, for example.

Although the preferred coordination unit provides for selection from among several separate signal cycle length timing means each of which may provide a different signal cycle length, obviously the number of selectable timing means may be reduced to selection between two timing means. This may be provided for by either making two of the timing means time the same signal cycle length or by reducing the available selection by reducing the number of timing means in the coordination unit. Various combinations of signal cycle length and various degrees of the same or different offsets are possible. As for example, three means for providing three different signal cycle lengths may be provided, each of the three cycle length means having associated therewith three different offset cam but, as among the cams of the same offset, each cam may be adjusted to a different degree of percentage of the offset. Thus for the same offset condition, selection of a timing means, may provide a different length signal cycle and each different length signal cycle may provide the same or a different degree or percentage of offset. However, the number of timing means may be reduced while the number of offset cams may remain the same and instead of selecting between different timing means, the same selecting circuitry, heretofore used for selecting between different timing means, may select between diiferent degrees of percentage of offset for the same offset condition by selecting between differently adjusted offset cams of the same offset condition. Further the coordination unit may be adjusted so that selection between several timing means may be made, with each timing means providing a different length time cycle but with the offset cams of the same offset condition adjusted to the same degree or percentage of offset.

Each of the selected timing means, which may be, for example, in the form of a motor, may rotate its associated offset cams at different speeds of rotation, and its selected associated offset cams may close a cam contact and operate a relay at one or more certain desired parts or percentage points of the traffic signal cycle so as to provide an output pulse from the coordination unit to the signal switching device.

The coordination unit associated with each signal switching device may also include one or more networks of contacts and circuitry each of which cascades from a plurality of individually operated single pole switches connected to a common power supply and through a network of relay contacts to provide an output from the coordination unit to the signal switching device when certain preselected output combinations are provided from the master controller. The single pole switches may be adjustable positioned to an open or closed position so as to supply output power to the signal switching device when the switch is closed and the selected output combination from the master controller is being received. As will be readily seen in the drawing, one or more switches may be positioned so that one or more output combinations from the master controller may provide the same output between the coordination unit and the signal sequence control unit.

The preferred embodiment of the coordination unit includes two such networks of manually operated, switch controlled, contacts and circuitry, although additional networks or one network may be provided if desired. Each network may be identical to the other and each may include as many as ten individual, manually controlled, locally adjustable switches. Of course, a pile-up of wafer switches may be used in lieu of the plurality of single pole switches in any one network if desired.

The signal switching device of the local controller may be in one of several different forms. Preferably, the signal sequence control unit may be in the form of a complete trafiic signal controller which is capable of independent operation and which may respond to control from a master controller. One form of signal switching device may include means for providing two or more splits or distribution of the trafiic signal cycle among the several signal phases, with any one split capable of being selected by the coordination unit according to adjustment of the single pole switches in the cascaded contact circuitry network and the output received from the master controller.

It is therefore an object of the present invention to provide an improved, actuated master controller of the electronic and electro-magnetic type, which is simplified, compact and relatively inexpensive.

Another object is to provide an improved master controller which may respond to two different traflic characteristics according to a predetermined relationship between the traffic characteristics and also according to the value of one or both traffic characteristics with the responding means individually and separately adjustable.

A further object is to provide an improved master controller which will provide response to various traffic conditions on a roadway and in particular to respond to a predetermined differential between the values of two different tramc flows and to provide other response to various preselected values of either or both traffic flows independent of the response to a predetermined differential.

An additional object is to provide an improved master controller in which selection may be made from one of three individually adjustable timing devices directly according to predetermined levels of traffic on a roadway or according to predetermined relationship between two traffic flows on a roadway or in accordance with pre selected combined conditions of traffic expressed in response to a predetermined relationship between traffic flows and a response to predetermined levels of traffic on a roadway.

A still further object is to provide an improved master controller in which one of three offset selections is made according to relative traiiic conditions on a roadway and in which one of three signal cycle length selections is made according to the level of one or more traffic flows, independent of relative traffic conditions.

Still another object is to provide an improved master controller whose components are included in one compact unit and in which such unit includes two identical traffic characteristic determining, measuring and comparing components, each component including a traffic characteristic determining and measuring unit, with each unit associated with multiple level response circuits or 11 deter-mining circuits individually adjustable with each response circuit with each trafiic characteristic measuring, determining and comparing component individually responsive to individually preselected levels of its associated traffic characteristic determining and measuring unit output with one response circuit of each determining, measuring and comparing component responsive to a pre determined differential between the two levels through application of the output of one of the two traflic characteristic determining and measuring units to the other traffic characteristic determining, measuring and comparing component so as to provide dual control of the differential response circuit and in effect make a difference level circuit out of one level response circuit for each determining, measuring and comparing component.

Still another object is to provide an improved master controller including two traffic characteristic determining, measuring and comparing components, each of which are identical, and are identically interconnected for determining, measuring and comparing each of two traflic characteristics and for selecting, according to the differential between such traffic characteristics one of severeral tralfic olfset conditions and for selecting, according to the level or value of either or both measured traflic characteristics, one signal cycle length from among several signal cycle lengths and for providing an output to local traffic controllers so that each local controller may select one tralfic plan from a plurality of traific plans preset in the local trafiic controller, including dilferent combinations of offset conditions and different signal cycle lengths according to trafiic conditions.

A still further object is to provide an improved master controller whose several components include one component by which selection of one of three timing devices is selected for timing a selected output of the master controller during which time the selected output of the master controller may not change.

Another object is to provide a traffic responsive masterlocal trafiic control system in which the master controller is a simplified, compact and relatively inexpensive electronic and electro-magnetic type master controller responsive to current trafiic demands and which provides an output to the several local controllers of the trafiic control system which may call for a coordinated plan of traific which may include a signal cycle offset, the degree of offset, signal cycle length and distribution of the signal cycle in accordance with current tralfic conditions and. in which the local controllers of the traffic control system may be either of the traffic actuated or non-traflic actuated type.

Other objects will be apparent from the following description and claims when read with reference to the drawings in which:

FIG. 1 is a block diagram of a plan view of a trafiic control system;

FIG. 2, including FIGS. 2 and 2a, is a diagrammatic view partly in block and partly in schematic form of one form of master controller;

FIG. 3 is a diagrammatic View of a simplified form of coordination unit which is part of a local traffic controller;

FIG. 4 is a diagrammatic view of a simplified form of signal sequence control unit which forms the other part of the local controller in the traflic control system;

FIG. 5 is a cam sequence chart illustrating one complete cycle of the cam driving mechanism.

FIG. 1BLOCK DIAGRAM. OF MASTER LOCAL TRAFFIC CONTROL SYSTEM Referring to FIG. 1 in more detail, a plan diagram of a traflic control system is represented, in block form, with a master controller 29 and two local controllers 21' and 22, with the master controller providing output, via grouped leads 23, to the local controllers 21 and 22 and also extending to other controllers in the traffic control system.

The master controller 20 which is surrounded by a broken line box may represent the master controller illustrated in circuit form in the combined FIGS. 2a and 2b with the circuitry in the left half of the broken line box 20 labeled FIG. 2a illustrated in FIG. 2a and the right side of the block diagram of box 20 labeled FIG. 2b illustrated in FIG. 2b. The local controllers 21 and 22 each including a box labeled FIG. 3 and FIG. 3 may represent the circuit diagram illustrated in FIG. 3 and FIG. 4 respectively. It will be noted that the local controller 22 is arranged for actuation by traflic on the cross streets through actuation of the detectors 22d and 22'd, while the local controller 21 is arranged for fixed time operation. Bot-h local controllers 21 and 22 may be of the type described and illustrated in the combined FIGS. 3 and 4. It will be noted in the particular reference to FIG. 4 that the controller therein illustrated may be operated as a fixed time unit or a trafiic actuated unit as desired.

A roadway 24, serving two way vehicle trailic, as illustrated by the arrow marked inbound in the upper part of the roadway and the arrow marked outbound in the lower part of the roadway is represented with two intersections 29 and 30. The vehicle trafiic that pass through the intersections 29 and/ or 30 is controlled by the signal lights represented by 31 and 32 respectively which signal lights are controlled by the local trafiic controller 21 and 22 respectively so that right-of-way is distributed between the main roadway 24 and the cross streets that make up the intersections of 29 and 30 respectively.

The rectangle 33 in the upper section of the roadway 24- and the rectangle 34 in the lower section of the roadway 24 each represent vehicle detectors in the respective lanes for detection of vehicles through actuation of the vehicles traveling in respective lanes and directions.

For the purpose of identification the traffic flow in the upper lane shall hereinafter be referred to as inbound traffic while the trafiic flow in the lower lane shall hereinafter be referred to as outbound traflic as indicated in the FIGURE 1.

As more fully described in the description below, the inbound vehicles traveling .in the upper lane of roadway 24, will actuate the detector 33 and according to the preferred embodiment, will cause closure of a pair of normally open contacts which will complete a circuit to energize a detector relay associated with one traflic characteristic determining and measuring unit of the master controller which will consider each actuation of the inbound vehicles and determine the characteristic as for example volume, of the inbound trafiic flow. The outbound vehicles, traveling in the lower lane of roadway 24, will actuate the detector 34 and will cause closure of a pair of normally open contacts to complete a circuit to energize a detector relay associated with the other, similar traflic characteristic determining and measuring unit of the master controller, which will consider each actuation of outbound vehicle traflic and de termine trafiic characteristics, for example the volume of the out-bound traific flow.

The detector devices 33 and 34 may be of the treadle type which are located in a roadbed, essentially containing a pair of open contacts which are closed by passage of a wheel or wheels of a vehicle thereover or may be of any other type, well known in the art, such as microwave or radiant energy vehicle detector or any other type of vehicle detector sensitive to sound, light, heat, pressure or magnetism, for example, which will cause closure of a set of normally open contacts upon actuation by a passing vehicle.

The grouped output leads 23 of the master controller 20, may, according to one embodiment, include five or more leads, for example, which will each individually extend to each local traffic controller in the trafiic control system. It may also be necessary to supply a common ground or return lead between the master controller and the individual local traffic controllers. This may increase the number of individual leads extending from the master controller to the local controllers but such return lead is omitted for convenience and simplification of the drawing.

In a traffic control system of the type represented, and of other similar types, it is desirable to coordinate operation of the individual controllers with the master controller and thus coordinate operation among the local controllers themselves, however, still maintaining certain of the operations of the individual local controller independcut, so that, for example, start of the traffic signal cycle of one local controller may be offset from the adjacent or next adjacent, or other local controller in the system so as to stagger commencement of the green or go signal between local controllers to provide a more uniform flow of traffic along the signalized roadway.

MASTER CONTROLLER OF FIGS. 2a-2b Referring now to FIGS. 2a and 2b, a diagram partly in schematic form and partly in block form is presented, of the preferred embodiment of a master controller with the combined figures, providing one form of the improved master controller.

The master controller illustrated in the combined FIGS. and 219 may be represented in FIG. 1 by the block 20 with FIG. 2a representing the circuitry found in the left section of block 20 labeled FIG. 2a and the FIG. 2b representing the circuitry that may be found in the right section of block 20 labeled FIG. 2b. Referring particularly to FIG. 2a a series of blocks are illustrated in the lower half of the drawing and are numbered 50', 51', 52', 53 and 54. The circuitry included in each of these blocks is identical to the circuitry illustrated in schematic circuit form in the broken line block directly above the respective solid line block and similarly numbered without the prime indication. Thus the circuitry in the broken line block 50 illustrates the circuitry that may be found in block 50 while the circuitry illustrated in the blocks 51, 52, 53 and 54 illustrates the circuitry that may be found in the blocks 51, 52', 53 and 54' respectively. Certain of the electrical components are illustrated in the lower blocks such as the relay 64' and the meter 121 etc. in block 50 and the relay 65' in block 51, the relay 66 in block 52, the relay 67' in block 53' and the relay 68 and triode 70 and interconnecting circuits 69 and 69 etc. in block 54 since the function of these relays although similar in response to the circuit to which they are a part as the corresponding relays and components illustrated above of corresponding numbers serve another and separate trafiic fiow.

Referring particularly to FIG. 2b, relays 65 and 65', 68 and 68', 66 and 66, 67 and 67', illustrated in broken line form, are merely displaced duplicates of the relays identically numbered in FIG. 2a.

FIGS. 20 and 2b have been presented in the manner shown in order to provide a more convenient description, however it should be understood that the improved master controller represented by the combined figures comprises a complete unit, the component parts of which serve to provide information from at least two sources and intercooperate to provide outputs for control of one or more local traflic controllers in a traffic control system or may be used to provide outputs for control of apparatus for control of the direction of trafiic flow in a lane or lanes of one or more roadways.

It should be understood that the following description of the circuit operations of the schematic circuit part of FIG. 2a also describes the circuit operations of the circuitry within the corresponding blocks in the lower part of the drawing except for the fact that the description of the circuitry in the upper blocks will respond to one traffic flow actuation, for example, in bound trafiic flow actuation while the circuitry in the block form of the corresponding block in the lower section of FIG. 2a will respond to another traific actuation, for example, outbound tratiic flow actuation. The two different trail-1c flows could be traffic that is proceeding along a roadway in opposite directions on the same roadway or may be on different roadways or may be the same traffic flow in the same direction on different roadways but any combination of different trafiic flows.

For the purpose of description it shall be assumed that the traffic flows to be sensed are trafiic flows traveling in a different direction, on the same two-way street, such as represented in FIG. 1 and referred to as inbound traffie flow and outbound trafiic flow.

Information from inbound traffic vehicles, in the form of a voltage pulse is obtained, by a closure of a pair of contacts through actuation by each inbound vehicle of the vehicle detector 33, illustrated in FIG. 2a as a pair of open contacts surrounded by a broken line box and labeled 33, which voltage pulse causes a detector relay 64 to become energized. The vehicle detector 33 in FIG. 2a may be similar to the vehicle detector 33 in FIG. 1.

Information from outbound traffic vehicles, in the form of similar voltage pulses, is obtained by a closure of a pair of contacts through actuation by each outbound vehicle of another vehicle detector 34, illustrated as a pair of open contacts surrounded by a broken line box labeled 34, which voltage pulse causes another detector relay 64 to become energized. The vehicle detector 34 in FIG. 2a may be similar to the vehicle detector 34 in FIG. 1.

TRAFFIC CHARACTERISTIC MEASURING COM- PONENTS FOR TWO TRAFFIC DIRECTIONS Essentially, the preferred form of master controller, illustrated in the combined FIGS. 2a and 2b includes two identical components (both components illustrated in FIG. 2a, one component represented in block form the other component represented in circuit form), each for providing a voltage respectively which is proportional to a characteristic of a traffic flow essentially measured and determined through actuation of the vehicle traflic in the respective traflic flow. It shall hereinafter be assumed that the traffic flow characteristic measured is the volume of tratfic. Each traffic volume measuring component may be adjusted respectively so that the certain number of vehicles, as desired, sensed over a certain period of time, the time period also being adjustable, will represent traific volume. The number of vehicles representing 100% traffic volume is determined by the road characteristics and represents the number of vehicles that may pass a particular spot during a certain period of time and still maintain substantially unobstructed flow of vehicle trafiic.

A direct current voltage, which is proportional to one volume of trafiic, for example, inbound trafii-c, is applied to a meter which may be calibrated to indicate trafiic volume in convenient terms. The voltage which is proportional to the volume of traffic is also applied to a determining circuit which is associated with the relay 65 and upon the volume of traffic or the proportional voltage reaching a predetermined minimum value, relay 65 is energized. Thus the volume of inbound traffic below or above a predetermined minimum value may be determined according to the condition of the relay 65.

The voltage, which is proportional to the volume of inbound trafiic flow, is also applied to the grid of a triode 70 in the component associated with the outbound traific volume while a comparable connection applies the voltage, which is proportional to the volume of outbound traflic, to the grid of a triode 70 in the component associated with inbound traffic volume.

Thus the volume of inbound trafiic, represented by a proportional voltage, provides partial control of the triode 70 via lead 69 by increasing or decreasing the bias of the triode 70 as the volume of inbound traffic, represented by the proportional voltage applied from lead 120, provides partial control of the triode 70- via lead 69' by increasing or decreasing the bias on the triode 70 as the volume of outbound traffic (i.e., the proportional voltage applied via lead 121, increases and decreases.

The cathode voltage of tube 71 is established by the cathode voltage of tube 76 by virtue of the joining of the two cathodes. The grid of tube 71 is at a voltage which varies according to the voltage representing inbound traffic volume (voltage on lead 120) but is at a constant value below the voltage that is proportional to the volume of inbound traffic.

Thus conduction of tube 71 is controlled via grid con= trol by an applied voltage that is at a constant value below the voltage that is proportional to inbound volume of traffic, and via cathode control by triode 70 which is itself controlled by grid control by an applied voltage proportional to outbound traffic volume. The circuit of triodes 70 will be recognized as a cathode follower.

DIFFERENCE CIRCUITS The circuit directly associated with, and effecting the grid of triode 71 and the circuit directly associated, with and effecting the comparable tube 71' in the block 54-, below the circuit drawing 54- are both referred to as difference circuits. The difference circuits 4 and 54 are adjustable, as desired, so that when the difference between the value of the two traific flows is at or exceeds a predetermined difference the difference circuit associated with the higher trafiic flow will respond. The predetermined amount or values over which one traffic volume must exceed the other trafiic volume in order to provide conduction of one of the tubes 71 or 71' is individually adjustable, as desired.

These interconnected circuits, although individually adjustable, may provide conduction of tube 71, in the inbound traffic volume component so that when both traffic volumes are sufficiently close so as not to exceed a predetermined difference between the two volumes, or when both trafi'ic volumesare substantially equal, relays 66 and 66 will both be deenergized and will provide for energization of relay 66 and deenergization of relay 66 when the volume of inbound traffic exceeds the outbound traffic volume by at least a predetermined value, as set in the difference circuit of tube 71'. Energization of relay 66 and deenergization of relay 66 is provided when the volume of outbound traiii-c exceeds the inbound trafiic volume by at least the predetermined value as set in the difference circuit of the comparable tube in the lower circuit.

With both volumes below their respective determined minimum volumes respectively the relays 65 and 66 of the inbound traffic volume component and the relays 65' and 66' of the outbound trafiic component may all be in a deenergized condition.

RESPONSE TRANSLATING COMPONENT OF MASTER CONTROLLER According to the preferred embodiment with the relays 65, 66, 65 and 66 deenergized the response translating component of the master controller, which translates the response combination of the several relays in the trafiic characteristic determining, measuring and comparing components may provide an output to the individual local controllers which may be interpreted by the local controllers to cycle free of any offset condition or may be interpreted to operate in average offset with each individual local controller interpreting such output according to the position of a selector switch as described below.

With either or both relays 65 and 65 energized and both relays 66 and 66' deenergized the translating component may provide an output to the local controllers which may call for average offset Of the local controllers without permitting a selection between free or average offset condition. With relays 65 and 66 energized and relay 66 deenergized, and with 65 energized or deenergized, the translating component of the master controller will provide an output to the local controllers which may call for inbound preferential offset and with relay 65 and 66 energized and relay 66 deenergized, and relay 65 energized or deenergized the response translating component of the master controller will call for outbound preferential offset.

The manner in which a call to the local controllers in the trafiic control system is accomplished is by providing for energization or deenergization, in combination, of the several output leads which extend from the master controller (grouped leads 23 in FIG. 1) to the local controllers in the traffic control system. A call is established by translation of the condition or response of the several relays of the trafiic characteristic determining, measuring and comparing components by the response translating component. The translated condition is expressed by energization or deenergization of the individual output leads, in combination.

Once a call to the local controllers has been established, a selected one of three timing mechanisms within the response translating component is initiated into operation and then electrically isolated from the selecting circuitry so that the established call will remain effective for at least a minimum period of time, after which the call may be changed, according to translation of the response of the several relays of the traffic comparing units to the traffic conditions then in effect.

It should be understood that the description of the circuit operations of FIG. 2a that follows and relates particularly to the circuit diagram in the upper portion of the figure, refers also to the circuitry within the blocks below, numbered with prime numbers, except that the detector 33 would be actuated by inbound traffic vehicles and detector 34 will be actuated by outbound trafiic vehicles on different lanes of the same two way street, for example, and that the adjustable parts of the inbound traffic component may be adjusted individually and separately from the adjustable parts of the outbound traffic components. Further as previously noted the reference level for the determining circuit 54 will be controlled by the voltage applied via lead 120' While the reference level for the difference circuit 54' will be controlled by the voltage level of the lead 120.

TRAFFIC MEASURING UNITSDESCRIPTION Let it be assumed that the master controller 20 in FIG. 1 represents the master controller illustrated in the combined FIGS. 2a and 2b and that the vehicle detector represented by 33 in FIGS. l and 2a is located in the upper lane of roadway 24 as shown in FIG. 1, so as to be actuated by the individual vehicles in the inbound trafiic flow and that the vehicle detector represented by 34 in FIGS. 1 and 2a is located in the lower lane of roadway 24 as shown in PEG. 1, so as to be actuated by the individual vehicles in the outbound flow.

Accordingly each time the vehicle detector 33 is actuated, its contacts are closed to complete a circuit to energize the inbound detector relay 64. Detector relay 64 will, upon energization close its contacts 80, which will illuminate detector indicator lamp 81, and will also close contacts 82 which may be used for other counting or indicating purposes as desired.

Energized relay 64 also opens contacts 83 and closes contacts 84. Between periods of actuation of detector 33, relay 64 is deenergized and contacts 83 are closed. During such closed periods bucket capacitor 85 is charged with a voltage tapped oif the potentiometer 86 at tap 8? in the cathode circuit of triode 90.

The plate of triode 90 is connected to a direct current (D.C.) source of approximately +300 volts, for example, represented by a plus in a square, and is normally conduct- 1 7 ing. Conduction of tube 90 is normally heavier than conduction of triode 91 partly due to the cathode circuit of tube 91 being connected through a neon tube 92 and resistor 93 to the +300 D.C. source, the neon tube 92 being a constant voltage drop device, and partly due to the grid control of tube 91 as described below.

The voltage at tap 89 is a percent-age of the voltage across the cathode to ground circuit including potentiometer 86 and resistor 94 which percentage of the total voltage is adjustable according to the position of tap 89 on potentiometer 86. The percentage of voltage picked oil by tap 89 of the potentiometer 86 from the cathode circuit of triode 90 is applied to capacitor 85, which is returned to ground, during closure of contacts 83 which are closed when relay 64 is in a deenergized condition.

Upon actuation of detector 33 thereby causing energization of detector relay 64 and subsequently the opening of contacts 83 and closure of contacts 84, the charge on capacitor 85 is bucketed" into tank capacitor 95 which capacitor is also returned to ground. The preferred embodiment provides for capacitor 95 to be substantially larger than the capacitor 85, and it has been found that capacitor 95 may be four times larger in capacitance than the capacitor 85 although other ratios may be used if desired.

The action of charging the capacitor 85 between actuations of detector 33 and the subsequent bucketing or transfer of the charge on capacitor 85 to capacitor 95 upon actuation of the detector 33 will, upon multiple actuations, attempt to accumulate the charge on the capacitor 95 while the accumulated charge is slowly discharging through resistor 96 and part of potentiometer 99 to tap 100 to junction 101, through resistor 102 through to the negative D.C. supply, of the order of 150 volts D.C., for eX- ample, represented by a minus in a square.

Adjustment of tap 100 provides for increase or decrease of resistance in the discharge circuit of capacitor 95 and may be used to calibrate the 100% value of volume for a desired number of vehicles. As for example, 1000 vehicles per hour may be equal to 100% volume or 800 vehicles per hour may be equal to 100% volume, according to the position of tap 100 on potentiometer 99.

The charge on capacitor 95 is also applied through resistance 103 through the grid of tube 91. This provides control of the conduction of tube 91, the amount of conduction through tube 91 being proportional to the charge on capacitor 95.

The cathode circuit of tube 91 is connected to the +300 volt D.C. source through junction 104, neon tube 92 and resistor 93 which holds the conduction of tube 91 below the conduction of tube 90.

It should be noted that the junction 101 in the cathode circuit of tube 91 is maintained at slightly above ground zero, and thus in absence of actuation, and absence of the bucketing of the charge from capacitor 85 into capacitor 95, over a substantial period of time, the capacitor 95 will substantially fully discharge through the discharging circuit described, but the potential on the capacitor 95 will not go below ground.

The voltage applied to the junction 104 may be measured by a volt meter, if desired, and may serve as a measure of the instantaneous volume of inbound traffic.

Thus the last described circuit provides for feedback from the cathode of tube 91 through a constant voltage drop, such as the neon tube 92 and a resistor 105 to the grid of tube 90 to provide cooperation between the tubes 90 and 91. This interconnection will provide for conduction of tube 90 at a variable rate but somewhat above conduction of tube 91 so that as the measure of volume of tralfic rises, which rise is represented by the amount of voltage applied at junction 104, the tube 90 will conduct more heavily and the charge applied to capacitor 85, which is a percentage of the cathode voltage of tube 90, will increase proportionally.

The increased charge on bucket capacitor 85 will be transferred to tank capacitor 95 and will become more highly charged with each individual bucketing action. With a higher charge on capacitor 95 a voltage applied to the grid of tube 91 through resistor 103 will increase and cause tube 91 to conduct more heavily, however the discharge circuit for capacitor 95 may balance otf the charge on capacitor 95 against the rate of discharge with the rate of discharge varied somewhat according to the amount of charge on the capacitor 95.

With tube 91 conducting at a higher rate the voltage at junction 104 is increased thus varying the potential applied to the grid of tube causing tube 90 to conduct at a still heavier rate.

With substantially frequent actuations, as by vehicles traveling at a relatively heavy volume of traflic flow, the charge-against-discharge rate of capacitor will balance off at a substantially high level, proportional to the volume of trafiic so that the voltage at junction 104 may increase or decrease linearly, proportional to the volume of traffic.

The voltage at junction 104 is applied to a calibration circuit 106 which is provided to select a volume averaging time, as desired, by adjustment of the selector switch 109. The selector switch is illustrated in position #1 which may average the volume, which is in the form of a D.C. voltage with zero to volts D.C. representing zero to 100% trafiic volume over a period of time, in position #1 being a shorter term average than position #2 and position #2 being somewhat shorter than position #3 and progressively increasing the term average up to position 6 which is the longest term average illustrated.

The long term average volume picked off by switch 109, diifers from the instantaneous volume at junction 101, and is applied to the capacitor 110 and to the grid of tube 112. The tube 112 is connected via its plate circuit to the cathode of tube 113 and thus provides a cascaded cathode follower. The plate of tube 113 is connected to the +300 D.C. voltage source with its grid circuit controlled by being connected to the +300 D.C. voltage source through resistor 114. The cathode of tube 112 is also connected to the +300 D.C. voltage source through the resistance 114 and further through a constant voltage device such as neon tube 115. This last described interconnection between tubes 112 and 113 sets the grid potential of tube 113 which in turn sets the plate voltage of tube 112. This essentially provides for elimination of the error apparent in any cathode follower operating over a wide voltage range, resulting from the fact that when the cathode voltage is low a relatively high negative grid voltage must be used to control the tube current, because there is a high plate voltage, as against the case in which the cathode voltage is relatively high and consequently the plate voltage is relatively low and the tube current is released, requiring low negative grid voltage.

The cathode of tube 112 is connected via resistor 116 to a minus 150 D.C. voltage source. The cathode voltage of tube 112 applied at junction 120 is a measure of the long term volume, the voltage being proportion-a1 to the volume of trafiic having actuated the detector device 33, averaged over a period of time selected by adjustment of a selector switch 109.

The voltage applied at junction 120 which is also referred to as lead 120 as also applied to a meter 121 which may be calibrated in convenient terms to indicate the value of traffic volume. The meter is connected to ground through a potentiometer 122 which may be used for calibration purposes. A diode 123 is connected between the junction 120 and ground to prevent the cathode circuit of tube 112 from dropping below ground potential.

The potential at junction 120 is also applied through resistor 124 to terminal 125 which terminal may be connected to an external recorder or other device as desired,

Certain graphic recorders may require that the terminal be first connected to an amplifier then to the recording device so that the load of the recorder will not load the circuit enough to effect the operation of tube 112. The potential at junction 120 or lead 120 is applied to match the resistors of the response determining circuits 51, 52 and 53 and to the difference circuit 54 via the lead 45 and from the lead 145 via lead 69 t the grid of tube 170' of the difference circuit 54.

RESPONSE CIRCUITSDESCRIPTION It will be noticed that the response circuits 51, 52 and 53 are substantially the same except that response circuit 52 includes in its energizing circuit for relay 67 a contact 65-1 which is operated by ener-gization of relay 65 of circuit 51 and circuit 53 includes in its energizing circuit for relay 68 a contact 67-1 which is operated by energization of relay 67 in circuit 52. This provides for a cascading response effect of the response circuits 51, 52 and 53 so that circuit 52 may only respond to the voltage on lead 120 only after response by circuit 51, resulting in-closure of the contact 65-1, and circuit 53 may only respond to the voltage on lead 120 after circuit 52 has responded to the voltage on lead 120 and has closed contact 67-1.

The contacts 65-1 and 67-1 each may be electrical gates which normally individually prevent operation of the response circuit of which it is a part and when operated by its controlling component permits operation of its response circuit.

Thus the three response circuits 51, 52 and 53 may be operated in sequential steps with circuit 51 first operated and closing its contacts 65-1 in response circuit 52 so that response circuit 52 may then operate after which its contact 67-1 may close permitting response circuit 53 to operate each as set by the individual adjustments.

Adjustment of one response circuit as for example 51, would be the same for adjustment of circuit 52 and circuit 53 except that under normal operations the response circuit 52 would be adjusted to a higher voltage value than response circuit 51 and response circuit 53 would be adjusted to a higher voltage value than circuit 52. Therefore it may be seen that although individually set and adjustable a description of the operation and adjustment of circuit 51 would substantially describe the operation and adjustment of circuit 52 and 53.

The volt-age potential on lead 120 is applied through matched resistors 126 and 129 with junction 130 between the matched resistors. The lower end of resistor 129 is connected to tap 131 on potentiometer 132 which potentiometer forms a part of a potential divider between a -150 volt D.C. source and ground, the potential divider including potentiometer 133, resistor 134, potentiometer 132 in parallel with potentiometer 135, resistor 136 and potentiometer 139.

The tap 131 may be adjusted so as to lift the triode 140 somewhat above the l50 volt D.C. supply, that is toward ground, or zero volts and, in effect hold the grid of triode 140 less negative than the negative voltage source.

A similar adjusting source is provided by matched resistors 141 and 142 being connected between potentiometer 135 via tap 143 from the cathode of tube 112 via lead 120.

The junction 130 is connected via normally closed make before-break contact 65-2 which is controlled by the relay 65, which is in the plate circuit of triode 140. With the cathode of triode 140 connected to ground, zero, a small negative bias on the grid of triode 140 will cause the triode to conduct.

By adjusting the tap 131 on the potentiometer 132 of the potential divider the potential at junction 130 may approach ground zero from a normally negative potential as the potential on lead 120 increases from approximately ground zero. In this manner control of the triode 140 may be maintained so as to initiate conduction of the triode 140 at a predetermined potential applied to the 20 junction and lead and through the resistor 126 to junction 130.

When the cathode voltage of tube 112, which represents the average volume of inbound traffic, and is applied through junction and lead 120 and hence through resistor 126 to junction 130, balances or overcomes the potential applied from the potential divider through resistor 129 to junction so that the potential as junction 130 is at substantially ground zero potential or above, in a positive direction, the triode 140 will conduct and cause energization of relay 65. Thus this balancing circuit may provide for conduction or response of triode 140 and therefore energization of relay 65 at a certain level of volume as determined by the setting of the tap 131, as desired.

Upon energization of relay 65 the contact 65-3 closes and after closing opens the contact 65-2. Thus a second balancing circuit including matched resistors 141 and 142 and tap 143 of potentiometer is connected from junction 144 so that adjustment may be made to have conduction of triode cease at a lower level of volume than that at which conduction had been initiated.

The potentiometers 133 and 130 of the potential divider circuit are provided for calibration purposes so that the controlling potentiometers 132 and 135 may be calibrated and provided with dials, to facilitate easy adjustment of the response circuit and operation of the entire unit. The energization of relay 65 also closes contact 65-1 which will permit conduction of the tube 140-2 when the potential at junction 130-2 is balanced or overcomes the potential applied through the potential divider and potentiometer so that the grid of tube 140-2 approaches a ground zero potential and tube 140-2 begins to conduct. Conduction of tube 140-2 will cause energization of relay 67 which will close its contact 67-1 and permit conduction of tube 140-3 when the potential at junction 130-3 is sulficiently negative or close to ground.

DIFFERENCE CIRCUITSDESCRIPTION The voltage potential on lead 120 is also applied as illustrated via leads 145 and 69 and resistors 146' to the grid of tube 70' of the difference circuit 54' of the outbound trafiic component associated with the outbound traffic flow. The lead 69 extends from the inbound traffic volume comparing unit shown here extending from the difference circuit 54 to the difference circuit 54' of the outbound traffic volume comparing unit and applies the potential carried by lead 120 which represents the volume of inbound traffic to the grid of tube 70' of the difference circuit 54'. A similar connection from the difference circuit 54 to the difference circuit 54 is provided as illustrated by the circuitry extending from the lead 120' and lead 145' to lead 69' which extends from the difference circuit 54' to the difference circuit 54 and through resistor 146 in difference circuit 54 to the grid of tube '70 thus applying the potential representing the volume of outbound trafiic to the grid of tube 70.

The described interconnecting leads between the two components provide control of the tube 70 in the inbound traffic volume component by the outbound traffic volume component and similarly, control the tube 70' in the outbound traflic volume component by the inbound trafiic volume component.

As may be seen in the inbound traffic volume component difference circuit 54, the plate of tube 70 is connected to the +300 volt D.C. source while the cathode of tube 70 is connected to the cathode of tube 71, both cathodes being connected in common through a resistance 149 to the minus 150 volt D.C. source.

When, for example, the outbound traflic volume increases and the potential, at junction 120' of the outbound traffic volume component increases proportionally. The potential at junction 120, applied to the grid of tube 70 of the inbound traffic component via lead 69 and resistor 146 causes conduction of the tube 70, the amount of conduction being proportional to the value of the potential applied to the grid of tube 70. The cathode potential of tube 70 will be applied to the cathode of tube 71 so that in order that the tube 71 may conduct, the grid potential of tube 71 must be at least at a predetermined value relative to the potential applied to the grid of tube 70.

The grid potential of tube 71 is controlled by a dilference circuit including potentiometers 150, 151 and 152 and resistor 153 connected between the potential applied via lead 120 and the minus 150 volt D.C .supply. Across the series connected potentiometers is a constant voltage drop source, such as neon tube 154. This parallel connected neon tube 154 is provided so that the voltage across the series connected potentiometers will remain constant while the potential at junction 120 varies with trafiic thus providing a circuit which may cause conduction of tube 71 when the potential of junction or lead 120 is at a given value below the potential at junction or lead 120.

The otentiometers 150 and 152 provide a calibration for the dials associated with the potentiometers 151 and 160. The potential pickoff a-t tap 155 is applied through normally closed make-before-break contact 66-1 of relay 66, through resistor 156 through the grid of tube 71. The dual control of tube 71 via the grid connection and the cathode connection, is provided so that conduction of tube 71 may occur when the potential applied from junction 120 of the inbound trafiic volume component is at a predetermined amount above the value at junction 120' of the outbound trafiic volume component. Thus the amount of conduction through grid control via outbound volume component of tube 70 will set the cathode voltage of tube 71 and the difference circuit of the inbound trafiic volume component will set the potential on the grid of tube 71 and thus through this dual control, the tube 71 will become conductive if the volume of inbound trairic is at or above the preset minimum difference between the outbound trafiic volume and the inbound traflic volume level.

The relay 66 is illustrated connected between the plate of tube 71 and the +360 volt D.C. source. When tube 71 is not conducting, relay 66 is deenergized and its contacts 66-1 is closed and contact 66-2 is open so that initiation of conduction of tube 71 may begin at the potential of tap 155 and cessation of conduction may occur at the potential of tap 159 of potentiometer 160, the potentiometer 160 being connected in parallel with the potentiometer 151. When the relay 66 is energized due to the tube 71 conducting, the contact 66-2 is closed and the contact 66-1 is open so that the potentiometer 160 and its tap 159 is substituted for the parallel potentiometer 151 and its tap 155 initially connected in the grid circuit of the tube 71. This provides that initiation of conduction of tube 71 may be set at one difference level as adjusted by the setting of tap 155 and cessation of conduction of tube 71 may be set at another difference level, as by adjustment of tap 159.

Thus, at a certain desired level of inbound traflic volume, as represented by the voltage level at junction and lead 123, the tube 149 may be caused to conduct and cause cnergization of relay 65 which may permit the tube 146-2 to become conductive and cause energizetion of relay 67 when the voltage level at junction 120 reaches a higher level. Energization of relay 67 may permit conduction of the tube 140-3 and energization of relay 68 at another and higher voltage level at junction or lead 120 as set by the tap 131-3.

As the volume of inbound trafiic increases from a low value to a higher value the response circuit 51 will be operated followed by operation of response circuit 52 at a higher level and followed by operation of response circuit 53 at a still higher traffic level thus providing response by the several response circuits in a cascading efiect as the volume of inbound trafiic increases.

Therefore it may be determined by the condition of the relays 65, 67 and 68 or 65', 67' and 68' the relative volume of inbound tratfic and the relative volume of outbound traflic respectively while the condition of relays 66 and 66 respectively may determine the relation between the inbound trafiic volume and the outbound traffic volume relative to a predetermined dilierence between the traffic volumes.

Although the individual response circuits of the comparison unit of one traffic characteristic determining measuring and comparing component may respond individually to preset minimum level of trafiic volume the actual traflic volume as for example inbound traflic volume may be read on the meter 121.

It will be noted that the difierence circuits 54 and 54 of the trafiic characteristic determining measuring and comparing components are arranged as constant diiterence circuits which will respond to a constant pro-set numerical ditference in volume, for example the number of vehicles per hour difference. Since the numerical difierence remains constant, the percentage differential between the two volumes or the percentage difference between the two volumes is reduced as both volumes increase from a lower value. Thus when both traffic volumes are low a greater percentage of difference between the two volumes will be required for operation of one of the difierence circuits whereas when both traific volumes are high a smaller percentage of difierence between the two tratfic volumes will cause operation of one of the difference circuits.

With the relays 65, 67 and 68 indicating response of the circuits 51, 52 and 53 respectively of the inbound trafiic characteristic determining, measuring and comparing component and the relays 54, 67 and 68 indicating response of the circuits 51', 52' and 53 respectively of the outbound trafiic characteristic determining, measuring and comparing component and the relay 66 of the difference circuit 54 indicating response via difference circuit 54 to a condition whereby the inbound traific is at least at a preset differential or more above the outbound traffic and energization of relay 66 indicating response of the difference circuit 54' indicating that the outbound trafiic volume is at or above a minimum differential with respect to the inbound traflic volume such response of the several relays may be translated by the circuitry illustrated in FIG. 2b, herein referred to as the response translating component of the improved master controller.

RESPONSE TRANSLATING COMPONENT.- FIG. 2b

Across the top of FIG. 2b represented in phantom form are the relays 65, 65', 66 and 66' over the left section of the drawing and relays 67, 67', 68 and 68' over the right section of the drawing with the individual relays representing the relays similarly numbered in FIG. 2a.

Referring particularly to the left section of FIG. 2b the relays 65, 65', 66 and 66, in phantom form, individually control the contacts 65-6, and 65-5, both normally open contacts, and 66-5 and 66-5, both normally closed contacts, respectively. The contacts 65-6 and 65'-5 are arranged in parallel due to the connection 169. The contact 66-5 is in the energizing circuit of the relay 171 when the lock relay 201 is deenergized. The contact 66'5 is in the energizing circuit of the relay 172 when the lock relay 201 is deenergized. When the relays 65, 65', 66 and 66 are deenergized, as for example during trafiic conditions in which both inbound tratfic flow and outbound traffic flow are below a minimum volume level as set by the adjustments of the response circuits 51 and 51 and neither volume level is sufiiciently above the other so as to be at or above a preset difference between the two volume levels and with the switch open as indicated, the relays 171 and 172 are deenergized as indicated. With the relays 65 and 65' deenergized the relays 67 and 67' respectively would be deenergized which in turn would hold relays 68 and 68' deenergized due to the cascading of the response circuits as previously described.

With the relay 171 deenergized its contacts 171-1, 171-2 171-4, 171-6, 171-8 and 171-9 are open and its. contacts 171-3 171-5, and 171-7 are closed. With relay 172 deenergized its contacts 171-2, 172-4, 172-6, 172-8. and 172-9' are open and its contacts 172-3, 172-5, and 172-7 are closed. The network of contacts associated with the bracketed terminals 1 through 7 provides power to one or more of the terminals according to the condition of the relays 171 and 172 in combination, except for terminal 7 through which is applied power at all times. The network of contacts associated with the indicator lamps 18.1, 182, 183 and 184 provide power to illuminate one or the other of the indicator lamps. The contacts 172-8 and 171-8 when closed individually supply power to the indicator lamps 185, 186 and 1 8.7 in the right half of the drawing so that one or the other of theseflamps may be illuminated. The contacts 171-9 and 172-9 individually control energization of the output lines 191 and 192, respectively which are two lines of the five grouped output lines generally labeled 23 in FIG. 1.

Thus when below minimum level traffic conditions are indicated by 51 the response of the trailic characteristic determining measuring and comparing component as by deenergization of the relays 6,5, 6,5. and 66 and 66., Power is applied to terminals and 6 from a source of positive supply through contact 171-3 and contact 172-5 to terminal 5 and also through contact 171-3 through lead 177 to terminal 6. Further indicator lamp 184 is illuminated via circuit from the source of supply through contact 172-7, 171-7 the indicator lamp 184 to ground. The contacts 171-8. and 172-8 are both open so that the indicator lamps 185, 186 and 187. are not illuminated. Further the contacts 171-9 and 172-9 are both open so that the output lines 191 and 19 2 of the grouped lines 23 are deenergized. Since the relays 6 5 and 65' individually respond to the circuit first responding to an increase of traffic volume of the associated traffic flow then when the relays 65 and 65 are both deenergized such response may be interpretated by the response translating com.- ponent to indicate that the traflic in both trafiic fiows are below a predetermined minimum value respectively. With both relays 66 and 66' in a deenergized condition indicating failure of response of both difference circuits 54 and 54', this may be interpretated as indicating that neither trafiic volume is sufficiently above the other to afiord any preferential treatment to any one trafiic flow over the other. Thus in such condition, as indicated, deenergization of the output lines 191 and 192 which may be used to control the offset of the local traffic controllers, may call for free operation of the local tratfic controllers.

Thus according to the condition of relays 65 and 65' and 66 and 66', one or another of several offset conditions may be called for through the condition of the output lines 191 and 192 of the grouped output leads 23 from the master controller.

With either or both relays 65 and 65 energized and both relays 66 and 66' deenergized both relays 171 and 172 would become energized through pull-in circuits in cluding either contact 65-5 or 65-5, contact 66-5, contact 201-1, the coil of relay 171 to ground, for relay 171 and either contact 65-5 or 65'5, contact 6 6-5, contact 201-3, the coil of relay 172 to ground for relay 172.

With both relays 171 and 172 energized contacts 171-2 and 172-2 are closed to apply power to terminals number 1 and number 2. Contacts 171-4 and 172-6 are also closed to illuminate indicator lamp 181. Contacts 171-9 and 172-9 are closed to energize the output leads 191 and 192 respectively.

With both output leads 191 and 192, energized a call by the master controller may be made to the local controllers for operation at an average offset condition.

The conditon of all four relays 65, 65', 66 and 66 deenergized would indicate that the response circuits 51 and 51' and the difference circuits 66 and 66 have not been operated due to the low traffic volume of both traffic flows.

It will be appreciated that although the output leads 191, 192, 193, 194 and 195 are shown completed through to ground by closure of their respective associated contacts, these leads may supply positive power when their respective contacts are closed or may operate relays or may have their respective contacts inverted so as to open a ground connection or open a positive supply connection.

It will also be appreciated that closure of switch 170, which may be manually operated or automatically operated serves to supply power as would be supplied via closure of contacts 65-5 and/ or 65-5 as above described. With switch closed response or lack of response by the relays 65 or 65 would not be interpreted by the response translating unit. Closure of switch 170 would eliminate free offset output conditions. With relays 65 and 66 both energized and relay 65' energized or deenergized and relay 66 deenergized (or with switch 170 closed regardless of the condition of relays 65 and 65 and relay 66 energized and relay 66' deenergized) the contact 66-5 will be open and the pull-in circuit for relay 171 will not be completed. However, contact 66-5 will be closed to complete the energizing circuit for relay 172.

With relay 171 deenergized and relay 172 energized, contact 171-3 will be closed and contact 172-4 will be closed to apply power to terminals number 6 and number 4. Contacts 171-5 and 172-6 will be closed to cause illumination of indicator lamp 182 and contact 171-9 will be open and contact 172-9 will be closed so that output lead 191 will be deenergized and lead 192 will be energized. This combination of output lead 191 deenergized and output lead 192 energized may call for the local controller to operate at an inbound offset condition, thus giving preference to inbound traffic over outbound traffic.

The condition of relay 66 energized and 66 deenergized would indicate that the difference circuit 54 has been operated and difference circuit 54 has not been operated. This condition indicates that inbound traflic volume is at least at or above the predetermined minimum value relative to outbound traffic volume.

With relays 65' and 66 both energized and relay 65 energized or deenergized and relay 66 deenergized (or with switch 170 closed regardless of the condition of the relay 65 and 65', and relay 66' energized and relay 66 deenergized) the contact 66-5 will be opened and contact 66-5 will be closed. The pull-in circuit for relay 172 will be open at contact 66-5 but the pull-in circuit for relay 171 will be completed and relay 171 will be energized and relay 172 Will be deenergized.

Under such conditions contact 171-2 and contact 172-3 and power will be applied to terminals number 1 and number 3. Contacts 171-6 and 172-7 will be closed to illuminate indicator 183 and contact 171-9 will be closed and contact 172-9 will be open so that output lead 191 will be energized and output lead 192 will be deenergized.

The combination of lead 191 energized and lead 192 deenergized may call for the local controllers to operate at an outbound offset condition, thus giving preference to outbound tralfic over inbound trafiic.

The combination of relay 66 energized and relay 66 deenergized would indicate that the difference circuit 54' has been operated and difference circuit 54 has not been operated. This condition indicates that outbound traffic volume is at least at or above the predetermined minimum value, relative to inbound trafiic volume.

Thus the master controller may call for one of several signal cycle offset conditions by its output leads 191 and 192 of grouped leads 23 (FIG. 1), and may in- 25 dicate that such call is being made by illumination of one of the indicator lamps 181 through 184.

At the same time as such call is being made power is applied to one or more terminals 1 through 6, with power constantly applied to terminal 7. Terminal number 1 has power applied to it when there is a call for average offset and when there is a call for outbound offset. Terminals numbered 2, 3 and 4 have power applied to them individually when there is a call for average offset, outbound offset and inbound offset, respectively. Terminal number 5 has power applied to it when there is a call for free operation. Terminal 6 has power applied to it when there is a call for inbound" offset and free operation.

A switch 173, illustrated open, is provided so that the terminals number 2 and number 5 may be joined and both terminals have power applied to them during a call for average offset and during free operation.

It will be noticed that the energizing circuits for the relays 175 and 176, other than the holding circuits do not include a source of positive power. Such power may be obtained through terminal number 7 if the jumper connections J-1, I-2, J-3 and/ or J-4 are connected such terminal. With jumper connections J-l and J-4- disconnected from the terminals and jumper connections J-2 and J-3 connected to terminal number 7 the con dition (energized or deenergized) of the relays 175 and 176 depend entirely upon the condition (energized or deenergized) of relays 67, 67', 68 and 68.

This connection may provide complete control of the relays 175 and 176 by the condition of the relays 67, 67', 68 and 6S and is but one of the several modes of operation of the master controller.

Let it be assumed that the jumper connections I-1 and I-4 are disconnected and the jumper connections ]-2 and .l-3 are connected to terminal number 7.

With the relays 67, 67', 68 and 68 deenergized the relays 175 and 176 will be or remain deenergized. With relay 175 deenergized its contacts 175-3 and 175-5 are closed and contacts 175-1, 175-2, 175-4, and 175-6 are open. With relay 176 deenergized, its contacts 176-3 and 176-5 are closed and contacts 176-1, 176-2, 176-4 and 176-6 are open.

SELECTION OF MOTOR DRIVEN CYCLE TIMERS BY RESPONSE TRANSLATING COMPONENT FROM RESPONSE CIRCUITS With both relays 175 and 176 deenergized indicator lamp 185 will be illuminated if either one or both contacts 171-8 and 172-8 are closed, and motor M-l will be supplied with power via contacts 176-5 and 175-5, cam C2/C3, the coil of the motor M-1 to ground. Further, with both relays 175 and 176 deenergized contacts 175-6 and 176-6 are open and the output leads 193 and 194 are deenergized. The combination of the relays 67, 67, 68 and 68 all being deenergized would indicate that response circuits 52, 53, 52 and 53 have not operated due to the failure of traific to increase to the level where response circuit 52 or 52' would operate. If the relay 171 or 172 or both were energized so as to close contact 171-$ and/or 172-8 the indicator lamp 185 would be illuminated to indicate that the motor M-l was selected for control of the signal cycle length. The offset condition may be indicated by illumination of indicator lamp 184, the free condition indicator lamp.

With either or both relays 67 and 67 energized and both relays 68 and 68 deenergized the energizing circuit for relay 175 may be completed from jumper connection I-Z through contact 67-5 or 67'-5, contact 201-5 the coil of relay 175 to ground. The energizing circuit for relay 176 will remain open and relay 176 will remain deenergized.

Energized relay 175 will close its contacts 175-1, 175-2, 175-4, and 175-6 and open its contacts 175-3 and 175-5. Indicator lamp 186 will be illuminated since contact 171- 8 or 172-8 or both contacts must be closed since relay 65 must be energized before relay 67 may be energized and relay 65 must be energized before relay 67' may be energized and therefore either one or both relays 171 and 172 would be energized and thus either or both contacts 171-8 and 172-8 would be closed. Therefore indicator lamp 186 would be illuminated for positive power through contact 171-8 or 172-8, lead 181, contact 176- 3, contact -2, the lamp 186 to ground.

Further, contact 175-5 is open to break the driving circuit for motor M-1 and contact 175-4 is closed to complete the driving circuit for motor M-2 from positive power, contact 176-3, contact 175-4 cam contacts 2/3 to motor M-l to ground.

Contact 175-6 is closed to energize output lead 193 and contact 176-6 is open holding output lead 194 deenergized.

Thus with relay 67 and/or 67' energized and relays 68 and 68' deenergized one or both trafl'lc comparing units have responded to a level of trafiic flow which is above the minimum traflic level (response of circuits 51 and/ or 51') and at or above the second level (response by circuits 52 and/or 52) but below the third level (set by adjustment of circuits 53 and 53). Further selection of motor M-2 and the combination of output 193 energized and 194 deenergized is provided to the local controllers which may be used to select a signal cycle length which may be different from that selected by other combinations of output lead conditions.

With relays 67 and 68 energized and/or relays 69 and 68' energized both relays 175 and 176 have their energizing circuits completed, with the energizing circuit for relay 175 completed as described above and with the energizing circuit for relay 175 completed from jumper I-3 via Contact 68-5 or 68'-5, contact 2111-7 the coil of relay 176 to ground.

Energization of relay 175 will reverse its contacts as previously described and relay 176 will close its contacts 176-1, 176-2, 176-4 and 176-6 and will open its contacts 176-3 and 176-5.

Closure of contact 176-2 completes a circuit to illuminate indicator lamp 187 and closure of contact 176-4 completes a circuit to drive motor M-3. Closure of contact 176-6 completes a circuit to energize output lead 194.

Therefore with energization of either one or both relays 68 and/or 68' the response translating unit may provide operation of the motor M-3 and the combined output leads 193 and 194 and illumination of lamp 187.

Thus according to the response of the response circuits 52 and 53 and 52' and 53 one of three motors is selected to drive a cam shaft and open and/or close cam contacts illustrated below the motor.

Each motor has its associated cam contacts, the cycle of which is illustrated in the Cam chart below FIG. 1, labeled FIG. 5.

As illustrated when in a common position cam contacts C1/C2 are open, 02/ C3 are closed C4/C5 are closed and C6/C7 are open. This condition is indicated by the shaded area in the cam chart. The length of time of one cycle depends upon the speed of the motor and the time required by each motor to complete a cycle may differ from the others. Therefore the cycle length may change according to the motor selected.

When a driving circuit for any one motor is completed it starts to drive its cam shaft while the other two motors remain still and their cam shafts and cam contacts remain still. As soon as the cam shaft of the driven motor is rotated out of the common position (the shaded area in FIG. 5), cam contacts C2/ C3 open and cam contacts C1/C2 close and cam contacts C4/C5 open and relay 261 becomes deenergized the contacts 261-1, 201-3, 201-5 and 201-7 start to open and contacts 201-2, 201-4, 201-6 and 201-8 close. After the latter set of contacts 201-2, 201-4 etc. close the former set of contacts 201-1, 201-3 etc. open.

The relays 171, 172, 175 and 176 would then be isolated from their energizing circuits and if any one or all of the relays had been energized those relays would remain energized through a holding circuit individual to each relay. If any one or all of the relays had been deenergized those relays would remain deenergized as the respective holding circuits would not have been completed.

When the relays 171, 172, 175 and 176 are isolated from their respective pull-in or energizing circuit the relays of the response circuits may change their condition Without any effect on the response translating unit.

The condition of the output leads 191, 192, 193 and 194 remains unchangeable so long as the relays 171, 172, 175 and 176 are in their isolated condition.

When the relays have become isolated, the driving motor closes its cam contacts C1/C2 and opens C2/C3. This opens the initial driving circuit of the active motor and closes a self driving circuit so that the motor is isolated from the contacts of the relays 175 and/ or 176.

After closure of the self-driving circuit of the active motor the cam contacts C6/C7 close and complete an energizing circuit for relay 205, through contacts of the initial driving circuit of the active motor.

Energized relay 205 closes its contact 205-1 which energizes output lead 195.

The active motor rotates the cam shaft, the speed of rotation depending upon the motor.

Thus an output from the master controller, to the local controllers may be maintained for a period of time depending upon the speed of rotation of the motor selected.

In the preferred form the master controller may select motor M1 when operating in free and/or when the value of at least one traffic flow is at or above the minimum value adjusted by the setting of response circuit 51 or 51 or both but not at or above the value at which the associated circuit 52 or 52' will respond. Motor M2 may be selected for operation when the volume of either one or both trafiic flows are sufliciently high to cause response by response circuits 51 and 52 and/ or 51' and 52'.

Motor M3 may be selected for operation when either one or both trafific flows are sufficiently high to cause response by the response circuits 51, 52 and 53 and/or 51, 52' and 53'.

Since response of the response circuits, in sequential steps, is made in response to increase of traffic flow and it may be desired to vary the signal cycle length according to the amount of traffic the motor M1 may cause rotation of its associated cam shaft in forty seconds, for example, while motor M-Z may cause rotation of its associated cam shaft in sixty seconds, for example and motor M3 may cause rotation of its cam shaft in eighty seconds, for example. Obviously other motor causing rotation of a cam shaft at other speeds may be used, as desired.

Thus the selection of an offset and signal cycle length output control may be maintained for at least a minimum time.

JUMPER CONNECTIONS AT MASTER CON- TROLLER FOR OFFSET AND CYCLE LENGTH SELECTION IN RELATION TO LEVEL RESPONSE CIRCUITS It may be desired to control the signal cycle length cooperatively so that at a desired offset condition the signal cycle length may change if the volume of traffic is sufiiciently high.

This type of coordinated control is provided for by connecting jumper J-2 to one of the terminals 1 through 6, as desired and connecting jumper I3 to one of the terminals 1 through 6 as desired. The terminals J-1 and I4 would be unconnected.

If, for example jumper connection J-2 was connected to terminal 3 then when power was provided via terminal 3 (when there is a call for outbound offset conditions) and traffic was sufficiently high to operate either or both relays 67 and/ or 67 the relay 175 could be energized and the output of the master controller would call for an outbound offset with the signal cycle length controlled by operation of motor M2.

Obviously various combinations of olfset condition over cycle length may be provided for, according to the setting of the jumpers. By connecting jumper J3 to terminal number 4 selection of motor M-3 may be obtained when there is a call for inbound offset and trafiic is sufficiently high to cause energization of relays 68 and/or 68.

If it is desired to provide a signal cycle length (selection of motor M2 or M-3) according to offset selection above the jumper connections J-1 and ]4 may be connected to one of the terminals 1 through 6.

Thus with jumper J-4 connected to terminal 3 then when power is applied to terminal number 3 (upon call for outbound offset conditions), the motor M2, for control of the signal cycle length, may be operated, therefore selection of the signal cycle length may be made according to the offset condition called for.

Of course, selection of a motor is also associated with selection of an output combination of the leads 193 and 194, as previously described.

Returning to the cam chart in FIG. 5, it will be noticed that just prior to completion of one complete cycle of the cam shaft the cam contacts C6/C7 open. This drops out relay 205 and causes contact 2051 to open thereby deenergizing output lead 195. Then cam contacts C1/ C2 open and cam contacts C2/C3 close and C4/C5 close. Closure of cam contacts C4/C5 cause energization of relay 201 which operates its contacts to electrically connect the relays 171, 172, and 176 to their respective contact circuit network which may maintain the respective relay energized or cause deenergization of any one or all of the relays, according to the condition of the response circuit relays 65, 65, 66, 66, 67, 67, 68 and 68.

It has been described how the various output lead combinations of energized and/ or deenergized leads from the master controller may be obtained. The plan diagram in FIG. 1 may represent how the output leads may be extended to the local controllers in the control system, as by grouped leads 23. It should be noted that a common ground return may be added to the grouped leads 23, if needed, however such return lead is omitted, for convenience.

The individual output leads may be extended to the local controllers in the control system, which may include a local coordination unit, block FIG. 3, of FIG. 1, shown in circuit form in FIG. 3 and block FIG. 4 of FIG. 1, shown in simplified form in FIG. 4.

LOCAL COORDINATION UNIT OF FIG. 3 AND MASTER SELECTION OF LOCAL CYCLE MOTORS Referring to FIG. 3 the grouped leads 23 represents the leads connected to the leads 191, 192, 193, 194 and extending from the master controller. Identical numbers are used to indicate connecting leads between the master controller and the local coordination unit.

The relays 175L, 176L, 171L and 172L in FIG. 3 are controlled by the leads 194, 193, 191 and 192 respectively between FIG. 2b and FIG. 3, and the relays in FIG. 3 in effect repeat the condition of the relays 175, 176, 171 and 172 respectively, located in FIG. 2b.

The relay 205L in FIG. 3 is controlled by the lead 195 between FIG. 2b and FIG. 3, which lead is controlled by the condition of relay 265 in FIG. 2b with relay 205 controlled by the cam contacts C6/ C7 of the operated motor.

Therefore it may be said that the relay 265L in FIG. 3 is controlled by the cam contacts C6/C7 of the operated motor in FIG. 2!).

As previously described the cam contacts C6/C7 are open during the time the offset, cycle length outputs and motor in FIG. 2b are selected by translation of the response of the relays of the comparing units. Thus during the time selection of offset and cycle length output and 29 cycle motor is made relay 205L in FIG. 3 is deenergized and its contact 205- is closed.

Since selection of offset and cycle length output, and cycle motor is expressed in the combination of relays 171, 172, 175 and 176 being energized and/ or deenergized and the relays 171L, 172L, 175L and 176L in FIG. 3 substantially repeat the condition of the relays 171, 172, 175 and 176 respectively in FIG. 2b then, when the selection of cycle motor M-l or M2 or M3 in FIG. 2b is made by the relays 175 and 176, selection of a corresponding cycle motor, M or M or M in FIG. 3 may be made by relays 175L and 176L in a similar manner. Thus when cycle motor M-l is selected by a combination of relays 175 and 176 to control the cycle of the master controller, motor drive M10 may be selected by the corresponding combination of relays 175L and 176L to control the cycle of the local coordination unit. Therefore it may be said that motor M-1 in the master controller in FIG. 2b may be associated with motor drive M-10 in the local coordination unit in FIG. 3; motor M-2 in FIG. 2b may be associated with motor drive M20 in FIG. 3 and motor M3 in FIG. 217 may be associated with motor M30 in FIG. 3.

Each motor drive in FIG. 3 drives a set of cam wheels, as for example motor M10 drives cam wheels C31, C32, C33 and C34, with motor drives M-20 and M-30 driving a corresponding set of cam wheels.

Each cam wheel is independently adjustable so that the cam lobe may be positioned as desired.

Along with selection of one of the three motor drives, by the condition of relays 175L and 176L, the set of cam wheels driven by the selected motor drive are also selected from the other two sets of cam wheels.

For example with both relays 175 and 176 in FIG. 2b deenergized, representing very light trafiic conditions, the relays 175L and 176L will also be deenergized. Contacts 5L-1, 5L-3, 5L-5 and 5L-7 are closed and 5L-2, 5L-4, 5L-6 and SL-S are open.

Closure of contact 5L1 completes a circuit from ground through closed contact 205-5, 5L-1, lead 310, motor M10 to positive power. Closure of contact 5L-3 prepares a circuit from ground to the cam contact 311, which will close when the lobe of cam wheel C32 is rotated and lifts the contact 311 from below. Closure of contact 5L-5 prepares a circuit from ground to the cam contact 312 which contact will be closed upon being lifted by the lobe of C33. Closure of contact 5L-7 prepares a circuit from ground to the cam contact 313 which contact will be closed upon being lifted by the lobe of C34.

The broken line 320 indicates that motor M-10 drives cam wheels C31, C32, C33 and C34. The arrows indicate the direction of rotation. Broken line 330 and broken line 340 each indicate that the cam wheels through which the respective broken lines pass are driven by motors M20 and M-30 respectively.

When the relay 175 in FIG. 2b, is energized, thereby causing energization of relay 175L in FIG. 3 and the relay 176 in FIG. 2b is deenergized thereby causing deenergization of relay 176L in FIG. 3 the combination of which may represent medium traflic conditions, then contacts 5L-2, 5L-4, 51-6 and 5L-8 would be closed and motor M20 would be selected for operation via a circuit from ground through closed contact 205-5, contact 5L-2, contact 6L-1, lead 325 to motor M-20 to positive power.

Closure of contact 5L-4 prepares a circuit from ground through contact 5L-4, 6L-3 to cam contact 321, contact 5L-6 prepares a circuit from ground through contact 5L-6, contact 6L-5 to cam contact 322 and contact 5L-8 prepares a circuit from ground through contact SL-S, contact 6L-7 to cam contact 323.

When both relays 175L and 176L are energized, as for example during heavy traific condition the motor M-30 and its associated cam wheels are selected for operation by completion of a circuit from ground through contacts 205-5, 5L-2, and 6L-2, lead 335, motor M-30 to posi- 30 tive power. Similarly, the set of cam wheels and their contacts, associated and driven by motor M-30 are made part of the prepared circuits via contacts 5L-4, 6L-4 to cam contact 331; contacts 5L-6, 6L-6 to cam contact 332 and contacts 5L-8, 6L-8 to cam contact 333.

Thus selection of a motor and its set of associated cams is accomplished for operation of the local coordination unit.

The speed of rotation of the individual motor of the local coordination unit may ditfer, one from the other and in the preferred form, the speed of rotation of the motor in the local coordination unit approximates the speed of the corresponding motor in the master controller.

As for example the speeds of rotation of motors M-l in FIG. 2b and M10 in FIG. 3 may be substantially equal, motors M2 in FIG. 2b and M-20 in FIG. 3 may be substantially equal and motors M3 in FIG. 2b and M-30 in FIG. 3 may be substantially equal.

Each motor M10, M-20, M-30 includes a cam wheel C31, C41, and C51 respectively in its respective set of cam wheels. The respective cam wheels each control a cam contact 301, 302, and 303 respectively. When closed, each cam contact 301, 302 and 303 respectively completes a self-driving circuit for the motors M-10, M-20 and M-30 respectively.

For example when the cam lobe on cam wheel C31 lifts cam contact 301 the contact opens and breaks the self driving circuit. The motor M-10 must then be supplied power by an alternate circuit in order to operate. The alternate power circuit includes the contact 205-5, controlled by relay 205L, which relay responds to lead 195 which lead is controlled by relay 205 in the master controller which is controlled by the cam contacts of the selected motor in the master controller, which cam contacts C6/C7 are employed for synchronization purposes.

If the motor M-10 is at rest (stopped with cam contact 301 open), and contact 5L-1 is closed, the motor M-10 will be initiated into operation upon closure of contact 205-5. This provides a coordination point or common starting time for selected motor drives in the local coordination unit. Contact 205-5 remains closed only so long as relay 205L remains deenergized. If the output via lead 195 fails then relay 205L would be deenergized and the local controller could operate without coordination. If the motor M10 is operating and rotates its cam Wheel so that the cam contact 301 opens when the alternate power circuit through contact 205-5 and 5L-1 is completed motor M-10 will continue to operate and the local controller, through the local coordination unit, will be in synchronization or coordination with the master controller.

As described one motor of three motors, and a full set of cam wheels is selected as a unit. Each set of cam wheels include a homing cam wheel such as C31, C41 and C51 an average offset cam Wheel, such as C32, C42 and C52, an inbound offset cam wheel such as C33, C43 and C53 and an outbound offset cam wheel such as C34, C44 and C54.

Selection of the motor and its set of associated cam wheels is made according to the condition of the relays L and 176L, which are responsive to the higher of the two trafiic flows. From the selected set of cam wheels, one cam Wheel may be selected according to the condition of the relays 1711. and 172L, which in effect repeat the condition of relays 171 and 172 respectively in FIG. 2b, which are responsive to the relation between the two traific flows.

For example with the master controller calling for average offset both relays 171 and 172 in FIG. 2b and therefore relays 171L and 172L will be energized and contacts 1L-1 and IL-3 will be open and 1L-2 and 1L-4 will be closed and contacts 2L-1 will be open and 2L-2 will be closed.

The last described contact circuitry will prepare a circuit for completion by the cam contact if one of the cam 

1. A TRAFFIC CONTROL SYSTEM HACING A MASTER CONTROLLER FOR SELECTION OF VARIOUS TRAFFIC CONTROL OUTPUTS FOR THE CONTROL OF THE LENGTH OF THE TIME CYCLE OF LOCAL TRAFFIC SIGNAL CONTROLLERS AND FOR CONTROLLING THE OFFSET OF SUCH TIME CYCLE WITH RESPECT TO A MASTER TIME CYCLE, SAID MASTER CONTROLLER COMPRISING TRAFFIC CHARACTERISTIC MEASURING MEANS FOR EACH OF TWO TRAFFIC DIRECTIONS ON A ROADWAY RESPECTIVELY FOR PROVIDING AN ELECTRICAL VOLTAGE OUTPUT RESPECTIVELY DEVELOPED FROM A SERIES OF VEHICLES IN TRAFFIC SENSED IN ITS RESPECTIVE DIRECTION, THE LEVEL OF SAID VOLTAGE OUTPUT REPRESENTING A CHARACTERISTIC OF TRAFFIC FLOW OF SAID VEHICLES AND BEING SUBSTANTIALLY CONTINUOUSLY VARIABLE OVER A RANGE OF VALUES PROPORTIONAL TO THE MEASURED TRAFFIC CHARACTERISTIC OF THE RESPECTIVE DIRECTION, A FIRST, A SECOND AND A THIRD VOLTAGE LEVEL RESPONSIVE MEANS INDIVIDUAL TO EACH MEASURING MEANS FOR OPERATING RESPECTIVELY IN RESPONSE TO FIRST, SECOND AND THIRD LEVELS OF A PROGRESSIVELY HIGHER ORDER OF THE RESPECTIVE SAID ELECTRICAL OUTPUT, EACH SAID LEVEL RESPONSIVE MEANS INCLUDING MEANS INDIVIDUAL THERETO FOR ADJUSTING THE LEVEL FOR SUCH RESPONSE, FOURTH RESPONSIVE MEANS INDIVIDUAL TO THE RESPECTIVE SAID MEASURING MEANS AND COMPRISING ADJUSTABLE DIFFERENCE CIRCUIT MEANS COUPLED TO BOTH SAID ELECTRICAL OUTPUTS FOR OPERATING INDIVIDUALLY IN RESPONSE TO THE LEVEL OF THE SAID ELECTRICAL OUTPUT OF THE ASSOCIATED SAID MEASURING MEANS BEING SUBSTANTIALLY IN EXCESS OF THE LEVEL OF THE OTHER SAID ELECTRICAL OUTPUT OF THE OTHER SAID MEASURING MEANS BY AN ADJUSTABLE PREDETERMINED DIFFERENCE, OFFSET CONTROL CIRCUIT MEANS SELECTABLE FOR PROVIDING ALTERNATIVE OFFSET TRAFFIC CONTROL OUTPUTS FOR OFFSET OF SAID TIME CYCLE OF THE LOCAL TRAFFIC SIGNAL CONROLLERS FOR ONE AND THE OTHER OF THE RESPECTIVE TWO TRAFFIC DIRECTIONS, RESPONSE TRANSLATING MEANS FOR SELECTING SAID TRAFFIC CONTROL OUTPUTS IN RESPONSE TO DIFFERENT COMBINATIONS OF OPERATION AND NON-OPERATION OF SAID SEVERAL RESPONSIVE MEANS FOR THE RESPECTIVE DIRECTIONS, SAID TRANSLATING MEANS INCLUDING MEANS RESPONDING TO THE OPERATION OF EITHER OR BOTH OF SAID FIRST LEVEL RESPONSIVE MEANS FOR THE RESPECTIVE DIRECTIONS AND ONE OR THE OTHER OF SAID FOURTH RESPONSIVE MEANS RESPECTIVELY FOR SELECTING ONE OR THE OTHER OF SAID OFFSET CONTROL OUTPUT CIRCUITS RESPECTIVELY, FIRST, SECOND AND THIRD INDIVIDUALLY SELECTABLE ROTARY TIMING MEANS INDIVIDUALLY ADJUSTABLE FOR PROVIDING FIRST, SECOND AND THIRD TIME LENTHS FOR SAID MASTER TIME CYCLE RESPECTIVELY WHEN SELECTED FOR CONTROL OF CYCLE LENGTH OF SAID TIME CYCLE OF SAID LOCAL TRAFFIC SIGNAL CONTROLLERS, AND SAID RESPONSE TRANSLATING MEANS FURTHER INCLUDING FURTHER MEANS COUPLED TO THE SECOND AND THIRD LEVEL RESPONSIVE MEANS RESPECTIVELY FOR TWO RESPECTIVE TRAFFIC DIRECTIONS FOR SELECTING FOR OPERATION SAID ROTARY TIMING MEANS IN RESPONSE TO DIFFERENT COMBINATIONS OF OPERATION OR NON-OPERATION OF SAID SECOND AND THIRD LEVEL RESPONSIVE MEANS, SAID FURTHER MEANS INCLUDING MEANS FOR SELECTING FOR OPERATION SAID FIRST ROTARY TIMING MEANS IN RESPONSE TO NONOPERATION OF SAID SECOND AND THIRD LEVEL RESPONSIVE MEANS, MEANS FOR SELECTING FOR OPERATION SAID SECOND ROTARY TIMING MEANS IN RESPONSE TO OPERATION OF EITHER ONE OR THE OTHER OF SAID SECOND LEVEL RESPONSIVE MEANS AND NON-OPERATION OF BOTH SAID THIRD LEVEL RESPONSIVE MEANS, AND MEANS FOR SELECTING FOR OPERATION SAID THIRD ROTARY TIMING MEANS IN RESPONSIVE TO OPERATION OF ONE OR THE OTHER OF SAID THIRD LEVEL RESPONSIVE MEANS. 